What are the classifications of sliding bearings!
1. Incomplete fluid lubrication bearings
Generally, lubrication is carried out in the form of lubricating grease, oil rope and dripping oil. The shaft diameter and bearing surface cannot get enough lubricant, and the liquid oil film is discontinuous. The structure is simple, the friction factor is large, and the wear is large.
(1) Radial sliding bearing
The gap between the shaft and the bearing shell cannot be adjusted, the structure is simple, and the shaft journal can only be assembled and disassembled from the shaft end. Generally used on machines with low speed, light load and allowable assembly and disassembly.
The gap between the shaft and the bearing shell can be adjusted, and the installation is simple. This method is often used when the machine is difficult to assemble and disassemble.
c. The bearing bush can swing appropriately in the bearing seat to adapt to the deflection of the shaft when it is bent. It is used when the drive shaft is skewed, and the joint bearing is suitable for bearing radial load at the junction of mutually swinging rods.
(2) Thrust sliding bearing
Commonly used flat thrust sliding bearings are in an incomplete fluid lubrication state due to the lack of liquid friction and need to be used together with radial bearings. It is used to bear the axial force.
(3) Powder metallurgy bearings (oil-impregnated bearings)
It is porous, and the oil is stored in the pores. It can automatically lubricate without adding lubricating oil for a long time to ensure normal operation. However, because its material is relatively soft, its load-bearing capacity is low. Used for light load, low speed and difficult to refuel situations.
(4) Plastic bearings
Compared with metal bearings, plastic bearings are lighter and easier to maintain. Good chemical stability, high wear resistance and fatigue resistance, and has vibration damping, sound absorption, self-lubricating, insulating and self-extinguishing properties. However, the thermal expansion coefficient is large, the thermal conductivity is low, the moisture absorption is large, and the strength and dimensional stability are not as good as metals. Used in places with low speed or good heat dissipation, the working temperature should not exceed 65℃, and the instantaneous working temperature should not exceed 80℃.
(5) Rubber bearings
It can absorb vibration and impact, and has good wear resistance and corrosion resistance in an environment with impurities, but its unit strength is lower than that of metal and has poor heat resistance. It is not suitable for use in high temperature and in contact with oil or organic solvents. The bearings used in the shaft tube of the ship must work in a damping and corrosive environment.
(6) Wooden bearings
Wood bearings are lightweight and inexpensive, can absorb impact, have low sensitivity to shaft deflection, but have low strength, poor thermal conductivity, moisture resistance, and wear resistance. It is used in light-load conditions that require vibration reduction, such as agricultural machinery disc harrow bearings, large ore pump bearings, etc.
2. Fluid lubricated bearings
(1) Hydrodynamic bearing
The journal and the working surface of the bearing are completely separated by an oil film. The dynamic pressure bearing must have: ①The bearing has enough speed; ②There is enough oil supply, and the lubricating oil has a certain viscosity; ③There is a proper gap between the journal and the bearing working surface. The multi-oil wedge dynamic pressure bearing can meet the high-precision rotation requirements of the shaft and has a long life. Used for high-speed and high-precision machinery, such as bearings for centrifugal compressors.
(2) Hydrostatic bearing
The journal and the bearing are completely separated by a load-bearing oil film with a certain pressure supplied from the outside. The formation of the oil film is not limited by the relative sliding speed, and has a large load-bearing capacity at various speeds (including zero speed). The shaft has good stability and can meet the high-precision rotation requirements of the shaft. The friction factor is small, the mechanical efficiency is high, and the life is long.
(3) Gas dynamic pressure and static pressure bearings
Gas dynamic pressure and static pressure bearings, using air or other gases as lubricants, have a small friction factor and high mechanical efficiency, which can meet the requirements of running. Gas bearings are used as gyro rotors and TV recorder bearings.
3. Non-lubricated bearings (plastic, carbon graphite bearings)
Operate without lubricating oil or grease. Less applications.
(1) Solid lubrication bearings
Use graphite, molybdenum disulfide, phthalocyanine dye, polytetrafluoroethylene and other solid lubricants for lubrication. It is used in special working conditions such as extremely low temperature, high temperature, high pressure, strong radiation, space, and vacuum.
(2) a. Magnetic current bearing Use magnetic fluid as lubricant;
b. Electrostatic bearing Use electric field to suspend the shaft;
c. Magnetic bearing The shaft is suspended by a magnetic field.